In vitro dissolution tests using aqueous, acid or alkaline media are carried out in formulation development and for controlling routine inter and intra batch variation of oral dosage forms such as tablets and capsules. Dissolution media which simulate gastrointestinal fluid may include surfactants and solubilisers such as sodium dodecyl sulphate (SDS) and non ionic surfactants. They mimic sink conditions for determining the dissolution profiles of poorly soluble compounds and drug formulations. Dissolution tests using different concentrations of sodium dodecyl sulphate may be employed to evaluate dissolution characteristics, as suggested, e.g., in a monograph on Griseofulvin capsules in “USP 24, page 789”. It is however recognised that SDS media are not physiologically relevant and may not forecast in vivo pharmacokinetic profiles reliably. Therefore modified or biorelevant gastrointestinal media comprising physiologically more relevant solubilisers such as lecithin, lysolecithin, bile salts, mono glycerides, fatty acids and mixed micelles thereof have been proposed to better simulate the fasted and fed states.